unassailable vs watertight

unassailable and watertight both are adjectives.

Word	Noun	Adjective	Verb	Adverb
unassailable	No	Yes	No	No
watertight	No	Yes	No	No

As adjectives, unassailable and watertight are synonyms defined as:

Other synonyms of unassailable include bulletproof, ironclad, unshakable.

unassailable (adjective)	watertight (adjective)
without flaws or loopholes	without flaws or loopholes
impossible to assail	not allowing water to pass in or out
immune to attack; incapable of being tampered with